.clock {
  text-align: center;
  margin-top: 200px;
}

.clock em {
  display: inline-block;
  line-height: 102px;
  font-size: 66px;
  font-style: normal;
  vertical-align: top;
}
.flip {
  display: inline-block;
  position: relative;
  width: 60px;
  height: 100px;
  line-height: 100px;
  border: solid 1px #000;
  border-radius: 10px;
  background: #fff;
  font-size: 66px;
  color: #fff;
  box-shadow: 0 0 6px rgba(0, 0, 0, .5);
  text-align: center;
  font-family: "Helvetica Neue"
}
.flip .digital:before,
.flip .digital:after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    background: #000;
    overflow: hidden;
    box-sizing: border-box; 
}

.flip .digital:before {
    top: 0;
    bottom: 50%;
    border-radius: 10px 10px 0 0;
    border-bottom: solid 1px #666;
}

.flip .digital:after {
    top: 50%;
    bottom: 0;
    border-radius: 0 0 10px 10px;
    line-height: 0;
}


.flip .number0:before,
.flip .number0:after {
    content: "0";
}

.flip .number1:before,
.flip .number1:after {
    content: "1";
}

.flip .number2:before,
.flip .number2:after {
    content: "2";
}

.flip .number3:before,
.flip .number3:after {
    content: "3";
}

.flip .number4:before,
.flip .number4:after {
    content: "4";
}

.flip .number5:before,
.flip .number5:after {
    content: "5";
}

.flip .number6:before,
.flip .number6:after {
    content: "6";
}

.flip .number7:before,
.flip .number7:after {
    content: "7";
}

.flip .number8:before,
.flip .number8:after {
    content: "8";
}

.flip .number9:before,
.flip .number9:after {
    content: "9";
}

.flip.down .front:before {
  z-index: 3;
}

.flip.down .back:after {
  z-index: 2;
  transform-origin: 50% 0%;
  transform: perspective(160px) rotateX(180deg);
}

.flip.down .front:after,
.flip.down .back:before {
  z-index: 1;
}

/*向上翻*/
.flip.up .front:after {
  z-index: 3;
}

.flip.up .back:before {
  z-index: 2;
  transform-origin: 50% 100%;
  transform: perspective(160px) rotateX(-180deg);
}

.flip.up .front:before,
.flip.up .back:after {
  z-index: 1;
}

.flip.down.go .front:before {
  transform-origin: 50% 100%;
  animation: frontFlipDown 0.6s ease-in-out both;
  box-shadow: 0 -2px 6px rgba(255, 255, 255, 0.3);
  backface-visibility: hidden;
}

.flip.down.go .back:after {
  animation: backFlipDown 0.6s ease-in-out both;
}

@keyframes frontFlipDown {
  0% {
      transform: perspective(160px) rotateX(0deg);
  }

  100% {
      transform: perspective(160px) rotateX(-180deg);
  }
}

@keyframes backFlipDown {
  0% {
      transform: perspective(160px) rotateX(180deg);
  }

  100% {
      transform: perspective(160px) rotateX(0deg);
  }
}

.flip.up.go .front:after {
  transform-origin: 50% 0;
  animation: frontFlipUp 0.6s ease-in-out both;
  box-shadow: 0 2px 6px rgba(255, 255, 255, 0.3);
  backface-visibility: hidden;
}

.flip.up.go .back:before {
  animation: backFlipUp 0.6s ease-in-out both;
}
@keyframes frontFlipUp {
  0% {
      transform: perspective(160px) rotateX(0deg);
  }

  100% {
      transform: perspective(160px) rotateX(180deg);
  }
}

@keyframes backFlipUp {
  0% {
      transform: perspective(160px) rotateX(-180deg);
  }

  100% {
      transform: perspective(160px) rotateX(0deg);
  }
}